Passive anode rods are a vital component to water heaters utilizing a steel tank. This sacrificial anode rod provides protection against tank corrosion through galvanic corrosion. The anode rod creates a galvanic current following between the anode and the cathode (the water heater tank) which it is electrically connected. The depletion of the anode rod caused by this galvanic circuit can be calculated by measuring this electric current value and knowledge of the anode rod properties. The measurement circuit components and algorithm used to measure the depletion of a water heater anode rod must be carefully selected to minimized introduced error. This paper describes the circuit and system tolerance stack-up to achieve accurate measurement of the anode rod depletion status.